In modern society with advanced technology, many technological products, for example, mobiles phones, personal digital assistants (PDAs), hand-held computers, and notebook computers, weed through the old to bring forth the new. The characteristic of convenient portability makes users exchange information, communicate with other people, access data, and accumulate knowledge anytime and anywhere. Thereby, the life quality and working efficiency of users can be enhanced. Accordingly, in order to make the usage time of said portable devices long, the application and charging of the batteries of the portable devices appear particularly important.
FIG. 1 shows a block diagram of a switching-mode charging apparatus according to the prior art. As shown in the figure, the switching-mode charging apparatus according to the prior art includes a sensing circuit 12′, a switching-mode charging circuit 14′, a control unit 16′, a battery module 18′, and a voltage converter 20′ (DC/DC). When a power adapter 22′ is plug to a portable device 10′ and the sensing circuit 12′ detects an output power of the power adapter 22′, a sensing signal is produced and is transmitted to the control unit 16′. In addition, the output power is transmitted to the voltage converter 20′ and the switching-mode charging circuit 14′. When the portable device 10′ is turned on, because of heavy loading, the voltage converter 20′ has to output larger output power. On the contrary, when the portable device 10′ is turned off or in sleep state, the output power the voltage converter 20′ has to output is smaller. When the portable device 10′ is turned on, slow charging mode is engaged; when the portable device 10′ is turned off or in sleep state, fast charging mode is performed. When the remaining capacity of the battery module 18′ is full, a system management bus (SMBus) is used to transmit a signal to the control unit 16′. When the control unit 16′ received the signal, a shutdown signal is transmitted to the switching-mode charging circuit 14′ for controlling the switching-mode charging circuit 14′ to stop charging the battery module 18′.
FIG. 2 shows a circuit schematic diagram of a switching-mode charging apparatus according to the prior art. As shown in the figure, the differences between the present figure and FIG. 1 are a first switching circuit 24′, a second switching circuit 26′, a resistor 28′, and the switching-mode charging circuit 14′. The first switching circuit 24′ is coupled between the power adapter 22′ and the switching-mode charging circuit 14′, and is closed according to the sensing signal. The second switching circuit 26′ is coupled between the switching-mode charging circuit 14′ and the battery module 18′, and is closed/opened according to an enable signal transmitted by the control unit 16′. The resistor 28′ is coupled between the first switching circuit 24′ and the switching-mode charging circuit 14′, and converts an output current of the output power to an output voltage.
The switching-mode charging circuit 14′ further includes a first switch 140′, a second switch 142′, an inductor 144′, a capacitor 146′, a resistor 148′, and switching-mode controller 150′. The first switch 140′ couples to the resistor 28′; the second switch 142′ couples to the first switch 140′ and the ground; the inductor 144′ couples to the first switch 140′ and the second switch 142′; the capacitor 146′ couples between the inductor 144′ and the ground; the resistor 148′ couples between the intersection of the inductor 144′ and the capacitor 146′, and the second switching circuit 26′.
The switching-mode controller 150′ couples between the first switching circuit 24′ and the second switching circuit 26′, and couples to the first switch 140′, the second switch 142′, and the control unit 16′. The switching-mode controller 150′ controls the first switch 140′ and the second switch 142′ according to the control signal for charging the battery module 18′ in fast or slow charging modes.
However, because the switching controller 150′ has to switch the first switch 140′ and the second switch 142′ continuously, the circuit thereof is complex. Besides, the inductor 144′ is adapted in the switching-mode charging circuit 14′, thereby power loss is huge. Furthermore, if the first switch 140′ and the second switch 142′ are located closely in circuit design, electromagnetic interference (EMI) problems tend to occur. Hence, circuit design is relatively complicated.
Accordingly, the present invention provides a novel charging apparatus of portable devices, which can prevent damage on the charging circuitry due to over-current or over-voltage. In addition, the novel charging apparatus of portable devices has low power loss, simple circuit design, and low cost.